1. Field of the Invention
The invention relates generally to a port closure device for differentially pressured vessels and, more particularly, but not by way of limitation, it relates to an improved closure apparatus which allows pressure differentiating communication with a vessel interior without use of a valve.
2. Description of the Prior Art
The prior art includes numerous types of sealing methods applicable to pressurized or evacuated vessels, but to applicant's knowledge, all such prior art devices utilize either a mechanical valve or a permanent type of seal such as glass fusion seal or a solder seal, such devices being more commonly known as vacuum tubes or tin cans, respectively.